This invention relates generally to spindle motors for magnetic disk drives, and more particularly the invention relates to a spindle motor having the necessary tolerance for driving disks of three and one-half inch and two and one-half inch diameters.
The technology relating to data storage in magnetic disk drives is following a continuing trend towards increased data storage density, reduced data storage device weight and size, and reduced power consumption. Factors motivating these trends include the increasing use of portable, lap-top and note-book size computers.
The advances in data storage technology and the reduced size of computers have lead to disk drives having smaller dimensions. Eight inch disk drives were followed by five and one quarter inch disk drives, and the latest portable computers use three and one-half inch and two and one-half inch disk drives. The Kato series of two and one-half inch disk drives of Conner Peripherals, Inc. (Assignee) will have the approximate size of a deck of playing cards and weigh only 5.5 ounces yet will have a 21.4 mega byte formatted capacity.
As the disk drives become smaller in size and weight, so do the disks. The reduced thickness of the disks leads to problems of disk warpage in mounting the disks to the spindle motors, which in turn, leads to problems in storing and accessing data on the disk surfaces. Typically, a clamp spring biases a disk into engagement with a flange on the hub of the spindle motor. Unless the surface of the flange meets stringent tolerances, less than 30 micro inch for a two and one-half inch disk, the disk can suffer warpage when mounted thereto.